#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
vector<LL>g[maxn];
LL col[maxn];
void dfs(LL u,LL fa,LL num){
    col[u]=num;
    for(LL i=0;i<g[u].size();i++){
        LL v=g[u][i];
        if(v==fa) continue;
        if(col[v]!=-1) continue;
        dfs(v,u,num^1);
    }
}
int main(void)
{
  cin.tie(0);std::ios::sync_with_stdio(false);
  LL t;cin>>t;
  while(t--){
    LL n,m;cin>>n>>m;
    for(LL i=0;i<n+10;i++) g[i].clear(),col[i]=-1;
    for(LL i=1;i<=m;i++){
        LL u,v;cin>>u>>v;
        g[u].push_back(v);g[v].push_back(u);
    }
    dfs(1,-1,1);
    LL ans=0;
    for(LL i=1;i<=n;i++){
        if(col[i]==0) ans++;
    }
    if(ans>n/2){
        cout<<(n-ans)<<"\n";
        for(LL i=1;i<=n;i++){
            if(col[i]==1){
                cout<<i<<" ";
            }
        }
        cout<<"\n";
    }
    else{
        cout<<ans<<"\n";
        for(LL i=1;i<=n;i++){
            if(col[i]==0){
                cout<<i<<" ";
            }
        }
        cout<<"\n";
    }
  }
return 0;
}
